Django 过滤器或 - q 对象性能与 I 性能

Question

什么会有更好的表现？哪个更快？这意味着较低的数据库负载？

Item.objects.filter(Q(creator=owner) | Q(moderated=False))

或者

result = Item.objects.filter(item.creator = owner) | Item.objects.filter(item.moderated = False)

Answer 1

这些应该生成相同的 SQL。我没有你的模型定义，但使用 auth.User模型你可以看到它是一样的:

>>> from django.contrib.auth.models import User
>>> from django.db.models import Q
>>> q1 = User.objects.filter(Q(is_staff=True) | Q(is_superuser=True))
>>> print(q1.query)
SELECT "auth_user"."id", "auth_user"."password", "auth_user"."last_login", "auth_user"."is_superuser", "auth_user"."username", "auth_user"."first_name", "auth_user"."last_name", "auth_user"."email", "auth_user"."is_staff", "auth_user"."is_active", "auth_user"."date_joined" FROM "auth_user" WHERE ("auth_user"."is_staff" = True OR "auth_user"."is_superuser" = True)
>>> q2 = User.objects.filter(is_staff=True) | User.objects.filter(is_superuser=True)
>>> print(q2.query)
SELECT "auth_user"."id", "auth_user"."password", "auth_user"."last_login", "auth_user"."is_superuser", "auth_user"."username", "auth_user"."first_name", "auth_user"."last_name", "auth_user"."email", "auth_user"."is_staff", "auth_user"."is_active", "auth_user"."date_joined" FROM "auth_user" WHERE ("auth_user"."is_staff" = True OR "auth_user"."is_superuser" = True)
>>> str(q1.query) == str(q2.query)
True